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A new study from South ��ֱ���� State University will investigate the age, growth, maturity and movement of Big Stone Lake's resurgent lake sturgeon population. 

Lake sturgeon have had a tumultuous history at Big Stone Lake, a freshwater a freshwater reservoir on the border between western Minnesota and northeastern South ��ֱ����.

Before settlers moved into the region, sturgeon could be found in many of the Northern Great Plains rivers and lakes. In fact, the fish was so abundant it was considered a nuisance to Big Stone's commercial fishermen in the late 1800s. Sturgeon, which can weigh over 200 pounds and reach over 8 feet in length, would cut through commercial fishing nets. Like other pests, they were hunted relentlessly and stacked on the shore like cord wood. Eventually, it was discovered sturgeon meat was oily, and the fish was burned as fuel for steamships.

Other factors, like dams, poor water quality and the popularity of caviar, contributed to the prehistoric-looking fish's demise. Around 1946, the last known sturgeon washed up on the shores of the 26-mile border lake.

In 2001, a group of Big Stone locals had a vision. Led by former Ortonville (Minnesota) fisheries supervisor Norm Haukos, the group wanted to return sturgeon to Big Stone.

The first step was to improve Big Stone's water quality. The lake had its fair share of water issues and its quality had dropped significantly throughout the 1900s. In the 1960s, there were even a number of communities dumping sewage into the lake.

But starting in 1983, a considerable amount of effort was put into improving Big Stone’s water quality. The Environmental Protection Agency provided grants that helped promote best management practices on the landscape and were used to construct improved ��ֱ���� waste management systems and updated sewage and wastewater treatment facilities in six communities within the Minnesota River watershed. These projects resulted in the lake's trophic status moving from hypereutrophic to eutrophic — a notable improvement in terms of water quality.

After years of planning and preparation, 6,500 sturgeon fingerlings were stocked into Big Stone in 2014. Additional classes of fingerings were stocked in each successive year.

More than a decade after the initial reintroduction, Big Stone appears to have a rebounding sturgeon population. But there are still many questions about the fish's long-term viability.

This fall, researchers from South ��ֱ���� State University's Department of Natural Resource Management and the U.S. Geological Survey’s South ��ֱ���� Cooperative Fish and Wildlife Research Unit will begin a three-year collaborative study with South ��ֱ���� Game, Fish and Parks and the Minnesota Department of Natural Resource Management in which they will look to better understand the age, growth, maturity and movement of sturgeon within Big Stone and the connecting waterways. The results of their work will provide valuable insight into managing sturgeon in Big Stone.

Tagging and data collection

Since the initial reintroduction in 2014, around 44,500 sturgeons have been stocked into Big Stone. Each fish has a small tag inserted into them before they are stocked. The tags have numbers that indicate the fish's stocking year.

These tags will provide Alison Coulter and Steven Chipps, two SDSU faculty members, with key data on the age-specific movement of sturgeon.

"Knowing the age of the fish is important because their survivorship after they are stocked could be driven by environmental factors or biological factors," Chipps, a professor and leader of the U.S. Geological Survey, South ��ֱ���� Cooperative Fish and Wildlife Research Unit, said. "We can go back and look at weather data (for example) to see what kind of environmental factors would have affected the particular stocking class year."

Annual precipitation is one of the environmental factors Chipps will examine. In previously published research, Chipps' team found that year-class strength, or the number of age zero lake sturgeon that survive and recruit to the overall population in a given year, was positively related to total annual precipitation at Voyageurs National Park.

Assistant professor Coulter, Chipps and a doctoral candidate will also catch around 50 sturgeon and place acoustic tags in them. Acoustic tags are cylinder shaped and ultrasonic, which means the frequency is above the hearing range of humans and fish. The tags emit a series of pings that can be "listened" to through an underwater microphone (known as a "hydrophone") and can identify if a tagged sturgeon is present.

"These tags will allow us to follow their movements," Coulter said. "This will allow us to better understand the habitats the fish are using within the lake."

Radio telemetry is often used in fish movement-related studies, but because sturgeon spend much of their time in deep water near the bottom of the lake, acoustic tagging is required.

"I'm interested to see the movement patterns of these fish," Chipps said. "Seasonally, where they will be? Especially the males. Are they congregating in certain areas? None of this information would be known without the ability to tag and track these fish."

Reproducing population

One of the biggest questions related to the restoration of Big Stone's sturgeon is the population's ability to naturally reproduce. Male sturgeon typically take between 8 and 22 years before they are sexually mature. Females take longer and have been found to reach maturity between 14 and 33 years old.

The researchers will conduct blood work during the spring to get a better idea of the reproductive status of male and female sturgeon.

"Given that lake sturgeon have been stocked since 2014, there could be some males out there that are mature," Chipps noted. "Males go to the spawning grounds before females. If there are areas in Big Stone Lake/Minnesota River that they are cuing in on, that could be potential spawning habitat."

When sturgeon are ready to spawn, they swim upstream to shallow, rocky riverbeds.

Movement restriction was one of the primary reasons for the sturgeon's initial decline. Throughout the 1900s, dams were added to the Minnesota River and connecting waterways which prevented sturgeon from reaching their preferred spawning grounds. This drastically limited their ability to reproduce.

According to Chelsey Pasbrig, a fisheries biologist with South ��ֱ���� Game, Fish and Parks, a considerable amount of habitat work has been completed on the Minnesota River to improve the sturgeon's ability to reach their preferred spawning grounds.

"In recent years, five dams have been removed on either the Minnesota River or its tributaries," Pasbrig said.

An additional project in the Browns Valley area will improve upstream connectivity and may potentially be a spawning area for sturgeon once they reach sexual maturity.

“Connectivity is always a good thing for fish,” said BJ Bauer, fisheries specialist for the Minnesota Department of Natural Resources. “It’s especially good for sturgeon.”

It’s expected that the Big Stone sturgeon population will eventually expand downstream into the Minnesota River and other waterways.

Coulter, who is an expert in fish movement, will assess the connecting waterways of Big Stone to better understand where the sturgeon's preferred feeding and spawning areas might be. 

"If we are able to document some reproduction, that would be a measure of success," Chipps said. "But in reality, what we really want to see in rebuilding this population is that young fish   that are naturally produced grow up to be adults and return to spawning grounds years later to produce another generation of fish."

As Coulter notes, this would be the ultimate success story at Big Stone Lake: a naturally reproducing population that needs little management.

"It's a long process," Chipps said. "Given that lake sturgeon reproduces at older ages compared to most fishes, it could take 30 years or more before you see that play out.”

Currently, a catch-and-release season for sturgeon is offered at Big Stone. There have been reports of sturgeon as large as 55 inches being caught in recent years.

As for a harvest season? While possible in the future, that’s still a long way down the road.